macbook photos not connecting with iCloud
In an effort to save space on my macBook pro 16, I copied all my photos to an external hard drive. Now, the MacBook photos album seems disconnected from iCloud. Even when I connect the external hard drive and open photos, the MacBook does not update the photos. I am signed in to the same apple account on all devices. When I click on the preferences in photo and click on the iCloud tab at the top, I get a message that 'iCloud features for photos are only available in the system photo library. After I did the transfer I found a comment that external hard drives could not be used as the system library - don't know where I saw this. If true, how do I re-establish the system library.
iPad Pro, iPadOS 14